In recent years, a safety system etc. for preventing accidents have been developed. Such a safety system is the one which obtains information about existence of vehicles and pedestrians around a self-vehicle and their locations through roadside apparatuses and vehicle-to-vehicle communications at specific areas including an intersection and displays support images indicating locations of those vehicles, pedestrians, etc. on a monitor screen.
As an example in this type of preventive safety system for preventing accidents, a driving support image provided during a right turn at an intersection is shown in FIGS. 7A and 7B. That is, when a self-vehicle comes to a driving support image display area of the intersection with a right-turn instruction displayed on a navigation screen 100 as in an illustration in FIG. 7A, a driving support image 110 is displayed as a pop up screen as shown in FIG. 7B. In the driving support image 110, moving images of the self-vehicle 111 and other vehicles 112 etc. near the intersection are shown as superposed images on a bird's-eye view of the intersection.
By referring to the driving support image 110 when turning right at the intersection, a driver can recognize an oncoming vehicle etc. existing at locations which are hard to check visually by the driver.
Also, Japanese Patent Document JP-A-2005-11252 proposes an information providing device for a vehicle which provides a right turn collision-avoidance support service capable of preventing a collision with another vehicle which cannot be sighted during a right turn at an intersection.
Conventionally, according to a display method for a driving support image by a bird's-eye view of an intersection such as the driving support image 110 shown in FIG. 7B, the bird's-eye view used as a background is shown such that a line of sight in the image is directed frontward of a self-vehicle's traveling direction. In such a bird's-eye view, the self-vehicle is shown in a lower portion near a center of the right-and-left direction (front side in the bird's-eye view), and a frontward area of the traveling direction of the self-vehicle is shown in a longitudinal upper portion from the position of the self-vehicle (depth direction in the bird's-eye view). Moreover, corresponding to the turn of the vehicle, the line of sight in the driving support image is also rotated. This is to make it easier for a driver to recognize intuitively the correspondence between a road state in the driving support image and an actual road state by making a field of vision on a screen correspond to the driver's field of vision and displaying it.
Further, according to the method for displaying, as a driving support image, not a bird's-eye view in which the intersection is overlooked diagonally from the back of the self-vehicle but a plane image in which the vicinity of the intersection is overlooked from above, conventionally, the driving support image is often displayed such that a traveling direction of the self-vehicle is aligned with a longitudinal direction near the center of the right-and-left direction of the screen. In this case, the self-vehicle is shown in a lower portion of the screen, and the frontward of the traveling direction of the self-vehicle is shown in the upper portion of the screen.
However, when displaying the image of the intersection relating to driving support by the above method on a horizontally wide monitor commonly mounted on a vehicle, since a display range of the horizontally wide monitor is narrow in a vertical direction, the range for showing an opposite lane and oncoming vehicles in the frontward area of the traveling direction of the self-vehicle is narrow. In the driving support during a right turn at the intersection, it is disadvantageous for a driver to have a narrow range for displaying items of information including the opposite lane and oncoming vehicles, such information being important for the driver to decide whether or not to make the right turn.
Particularly, in a three-dimensional expression like the bird's-eye view in consideration of perspective representation, the frontward area in the traveling direction of the self-vehicle is displayed smaller in the upper portion of the screen in the depth direction in the bird's-eye view as it is shown farther from the self-vehicle. Therefore, in the driving support image during the right turn at the intersection, the oncoming vehicle is displayed small, which is hard to recognize for the driver. Moreover, when there are two or more oncoming vehicles in a row, rear vehicles are hidden by front vehicles on the screen. Therefore, it is sometimes difficult for the driver to recognize the presence of rear vehicles or a space between oncoming vehicles. Therefore, in the bird's-eye view in which the intersection is overlooked diagonally from the back of the self-vehicle and shown three-dimensionally, the problem described above is remarkable.